front: fix nge import when there is only one step

front/src/applications/operationalStudies/components/MacroEditor/osrdToNge.ts

@@ -244,12 +244,16 @@ const importTimetable = async (
   );
   const trainSchedules = await trainSchedulesPromise.unwrap();
 
+  const filteredTrainSchedules = trainSchedules.filter(
+    (trainSchedule) => trainSchedule.path.length >= 2
+  );
+
   const searchPayload = buildOpQuery(infraId, trainSchedules);
   const searchResults = searchPayload ? await executeSearch(searchPayload, dispatch) : [];
 
   const resource = {
     id: 1,
-    capacity: trainSchedules.length,
+    capacity: filteredTrainSchedules.length,
   };
 
   const nodes: NodeDto[] = [];
@@ -300,7 +304,7 @@ const importTimetable = async (
   const DTOLabels: LabelDto[] = [];
   // Create one NGE train run per OSRD train schedule
   let labelId = 0;
-  const trainruns: TrainrunDto[] = trainSchedules.map((trainSchedule) => {
+  const trainruns: TrainrunDto[] = filteredTrainSchedules.map((trainSchedule) => {
     const formatedLabels: (LabelDto | undefined)[] = [];
     let trainrunFrequency: TrainrunFrequency | undefined;
     if (trainSchedule.labels) {
@@ -369,7 +373,7 @@ const importTimetable = async (
 
   let trainrunSectionId = 0;
   const nodesByOpId = new Map<string, NodeDto>();
-  const trainrunSections: TrainrunSectionDto[] = trainSchedules
+  const trainrunSections: TrainrunSectionDto[] = filteredTrainSchedules
     .map((trainSchedule) => {
       // Figure out the node ID for each path item
       const pathNodeIds = trainSchedule.path.map((pathItem) => {